1. Field of the Invention
The present invention relates to a novel process for the preparation of ethyl acetate from acetic acid and ethylene. The invention more particularly relates to the preparation of ethyl acetate by reacting acetic acid with ethylene in the vapor phase in the presence of a special type of ion exchange resin.
2. Description of the Prior Art
It is well known to the art to react acetic acid with ethylene in the presence of acid catalysts to obtain ethyl acetate. A certain number of catalysts and operating conditions have been proposed in the literature. Certain authors have tested various catalysts for carrying out the present reaction in the vapor phase, for example, Y. Murakami, T. Mattori and H. Uchida, Kogyo Kagaku Zasshi, Vol. 72, pages 1,945-1,948 (1968). In particular, Murakami et al compared the catalytic activity of mixtures of silicotungstic acid and silica gel, and of phosphoric acid and kieselguhr, with that of certain ion exchange resins such as AMBERLITE IR 120 B and AMBERLYST 15. The first is of the gelantinous type, while the second is of the macroporous type, and both are marketed by Rohm and Haas. Murakami et al concluded that both phosphoric acid on kieselguhr and AMBERLITE IR 120 B have virtually no catalytic activity in the present reaction. Furthermore, they demonstrated that, although the catalysts based on silicotungstic acid have an appreciable initial activity at relatively high temperatures, such catalysts are deactivated after only a few hours of operation. The efficiency of these catalysts in the present reaction is virtually zero at temperatures below 150.degree. C., while at high temperatures, they cause the formation of acetone. Murakami et al showed that, although AMBERLYST 15 is the most efficient catalyst in the present reaction, it, too, becomes deactivated after only a few hours at the temperature required by the reaction.
Therefore, the catalysts of the first type are unsuitable for carrying out the present reaction in the gas phase because of their low activity, and use of the second type of catalysts, the resins suggested by the earlier prior art, has failed because of their instability and rapid deactivation at the temperatures required for the present reaction to proceed satisfactorily. In conclusion, the proposals of the prior art for preparing ethyl acetate by reacting ethylene with acetic acid in the vapor phase have not proved satisfactory on an industrial scale.
It is well known to the art that ethyl acetate is one of the most commonly used esters in industry because of its exceptional solvent properties. Therefore, it would be highly desirable to have available catalysts for the preparation of this ester by the present process which are both more efficient and more stable than the prior art catalysts. The potential value of having available such catalysts has already been widely recognized.